各种数据库的比较
1. sql区别以及对应关系。mysql oracle DB2 sqlserver Derby
XXXXX blob XXXXX image XXXXX
XXXXX clob XXXXX text XXXXX
date date date datetime date
2. create table
1. Oracle: default value should be ahead of [ column_constraint [, ... ]
CREATE [ [ LOCAL ] { TEMPORARY | TEMP } ] TABLE table_name ( { column_name data_type [ DEFAULT default_expr ] [ column_constraint [, ... ] ] | table_constraint } [, ... ]).....
Such as: name varchar2(16) default '' NOT NULL
3. how to insert "'" into databse with executing sql statement.
1.MSSQL: Use two "'" ("''") instead of "'".
4. How to insert a Date(datetime) field?
Mysql date '2004-01-01'
Oracle date to_date('01-01-2004', 'DD-MM-YYYY')
DB2 date '2004-01-01 00:00:00.000'
Sqlserverdatetime'2004-01-01'
Derby date '2004-01-01 00:00:00.000'
5. How to get current date&time?
ORACLESELECT SYSDATE FROM DUAL
DB2 SELECT CURRENT TIMESTAMP FROM SYSIBM.SYSDUMMY1
SQLSERVER SELECT GETDATE() FROM TABLE
MYSQL mysql> select now();
mysql> select sysdate();
mysql> select curdate();
mysql> select current_date;
mysql> select curtime();
mysql> select current_time;
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